[PATCH] Revert "drm/virtio: drop prime import/export callbacks"

[Gerd Hoffmann]

On Tue, Apr 23, 2019 at 12:55:07PM +0100, Emil Velikov wrote:
> On Tue, 23 Apr 2019 at 09:05, Gerd Hoffmann <kraxel at redhat.com> wrote:
> >
> >   Hi,
> >
> > > > The DRI3 code extensively uses prime_handle_to_fd and
> > > > prime_fd_to_handle for self-import.
> >
> > The callbacks are not used for self-import.
> >
> Userspace converts from it's own handles to a dmabuf fd and vice-versa.
> I assumed that's called self-import, is it not?

self-import is importing a dma-buf into the driver which created it.

drm_gem_prime.c has a shortcut for that, it'll just increase the gem
reference count instead of going though a full-blown export/import.

The prime_handle_to_fd and prime_fd_to_handle callbacks are only needed
for the non-self-import case, where the other driver needs/provides a
scatter list.

cheers,
  Gerd